One type of IR-CCD image sensor which has been developed includes a plurality of Schottky-barrier IR detectors arranged in rows along the surface of a substrate of single crystalline silicon. Between the rows of the detectors are CCD registers each of which is coupled to a row of IR detectors to receive the detected charge signal from the detectors. The CCD registers are coupled to an output CCD register to which the detected signal is transferred. Such an image sensor is shown and described in the article of W. F. Kosonocky et al., entitled DESIGN AND PERFORMANCE OF 64.times.128 ELEMENT PtSi SCHOTTKY-BARRIER INFRARED CHARGE-COUPLED DEVICE (IRCCD) FOCAL PLANE ARRAY, published in SPIE, Volume 344, Infrared Sensor Technology (1982), pp 66-77. In this type of array each detector includes a layer of a conductive material, such as platinum silicide or palladium silicide, along the surface of the silicon substrate and forming a Schottky-barrier junction with the substrate. Around and contacting each of the conductive layers is a guard ring, which is a region within the silicon substrate of a conductivity opposite to that of the substrate. Also around each of the detector areas and between adjacent guard rings is a channel stop, which is a region within the substrate of the same conductivity type as but of higher conductivity than that of the substrate. The guard rings serve to reduce fields at the edge of the Schottky-barrier junctions and the channel stops serve to prevent leakage of charge between adjacent detector areas and between each detector area and the adjacent CCD register to which the detector is not connected. Also, transfer gates extend along the row of detectors between the detector and its adjacent CCD register to transfer the charge in the detector to the CCD register. The transfer gate is in the form of a strip of conductive material, such as conductive polycrystalline silicon, which is insulated from the substrate by a layer of silicon oxide.
A problem with the above-described structure is that the peripheral elements, such as the channel stops and transfer gates, take up a relatively large amount of space over the surface area of the substrate. To obtain better resolution of the images detected, it is desirable to provide the image sensor with a larger number of detector elements. However, it is also desirable to maintain the overall size of the sensor as small as possible. Also, it is desirable to form an image sensor which has a high fill factor, which is the ratio of the active detector area to the total area of an image cell. Reducing the dead space between and around the detector areas, which is where the channel stops and transfer gate are located, will provide both a higher fill factor and minimize the overall size of the image sensor.